Deoxygenated fuel-cooled environmental control system pre-cooler for an aircraft

ABSTRACT

A fuel based thermal management system according to the present invention includes a fuel stabilization system which permits the fuel to exceed the traditional coking temperatures. An air-to-fuel heat exchanger operates as an environmental control system (ECS) pre-cooler such that the heat from the engine compressor bleed air is rejected into the fuel to maintain engine operating efficiency.

BACKGROUND OF THE INVENTION

The present invention relates to a thermal management system, and moreparticularly to a thermal management system which utilizes a fuelstabilization unit with a fuel-air pre-cooler for an aircraftenvironmental control system.

Aircraft utilize sophisticated Thermal Management Systems (TMS) forcomponent and environmental thermal management. An environmental controlsystem (ECS) provides a supply of conditioned air to an enclosure, suchas an aircraft cabin and cockpit. Conventional ECSs have utilized an aircycle cooling system which is in a heat exchange relationship with aliquid loop. The liquid loop typically cools other heat loads such asavionics packages. Interaction between the air and liquid subsystems isrelatively complex.

In one conventional ECS, a flow of bleed air is drawn from anintermediate or high pressure engine compressor section of a gas turbineengine. Although effective, a penalty paid for the use of bleed air is areduction in operating efficiency of the engine from which the air isbled. Furthermore, the bleed air is often above 700 degrees Fahrenheitand must be pre-cooled to below 450 degrees Fahrenheit in an enginepylon mounted air-to-air heat exchanger prior to being communicatedthrough the aircraft wing and into the ECS. The cooler air communicatedto the air-to-air heat exchanger is fan bypass airflow drawn from a fansection of the of the aircraft engine. The fan bypass airflow is airdrawn from the fan duct of a gas turbine engine which further reducesthe operating efficiency of the engine.

Accordingly, it is desirable to provide an effective, lightweightthermal management system for an aircraft ECS which minimizes reductionin engine operating efficiency.

SUMMARY OF THE INVENTION

A fuel based thermal management system according to the presentinvention includes a fuel stabilization system which permits the fuel toexceed the traditional coking temperatures. An air-to-fuel heatexchanger operates as an environmental control system (ECS) pre-coolersuch that the heat from the engine compressor bleed air is rejected intothe fuel. The deoxygenated fuel air-to-fuel heat exchanger minimizesdrawing of engine bypass airflow with a conventional air-to-airpre-cooler which would otherwise decrease engine operating efficiency.

The present invention therefore provides an effective, lightweightthermal management system for an aircraft ECS which minimizes reductionin engine operating efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

FIG. 1 is a general block diagram of a thermal management systemaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a general perspective view of a fuel based thermalmanagement system (TMS) 10 for an energy conversion device (ECD) 12. TheTMS includes a fuel circuit 14 and an environmental control systemcircuit 16.

A fuel stabilization system (FSU) 18 receives a liquid fuel from a fueltank system 20 (illustrated schematically). It should be understood thatthe location of the FSU 18 represents only one of many possiblelocations, and that the FSU may be located in other locations whilestill deoxygenating the fuel to be advantageously utilized at highertemperatures with high temperature resistant components.

The ECD 12 may exist in a variety of forms in which the fuel, at somepoint prior to eventual use for processing, for combustion or for someform of energy release, acquires sufficient heat to support autoxidationreactions and coking if dissolved oxygen is present to any significantextent in the fuel. One form of the ECD 12 is a gas turbine engine, andparticularly a turbofan engine illustrated schematically which includesa fan section 22, a compressor section 24, a turbine section 26, and acombustor section 28.

The fuel is typically a hydrocarbon such as a liquid jet fuel. The FSU18 includes a fuel deoxygenation system 30 which permits the fuel toremain stable at much higher temperatures without coking by removingdissolved oxygen from the liquid fuel which enables higher temperatureloads to reject their heat to the fuel. It should be understood thatvarious deoxygenation systems will benefit from the present invention.For further understanding of a fuel deoxygenator system and associatedcomponents thereof, attention is directed to U.S. Pat. Nos. 6,315,815and 6,709,492 which are assigned to the assignee of the instantinvention and which are hereby incorporated herein in their entirety.

The fuel in the fuel circuit 14 serves as a coolant for theenvironmental control system (ECS) circuit 16 to absorb thermal energytherefrom prior to the elevated temperature fuel being communication tothe combustor section 28 of the ECD 12. In general, heating of the fuelincreases efficiency of the ECD 12. The deoxygenation system 30 permitsfuel to accommodate temperatures upwards of 900 degrees Fahrenheit.

A liquid-to-air heat exchanger system 32 is located at an intersectionbetween the circuits 14, 16. The liquid-to-air heat exchanger system 32is embodied herein as an ECS pre-cooler, however, other subsystems whichrequire thermal management will likewise benefit from the presentinvention and that other heat exchanger subsystems may be incorporatedinto the TMS 10. It should be understood that various precautions may bepreferably taken due to the close proximity of the compressed air withthe high temperature deoxygenated fuel, however, such precautions arewell within one of reasonable skill in the thermal management art.

The ECS circuit 14 receives compressed air from the compressor section24 of the ECD 12. The compressed air is communicated through theliquid-to-air heat exchanger system 32 prior to communication to anaircraft cabin 34 through an aircraft environmental control system (ECS)36. The liquid-to-air heat exchanger system 32 preferably reduces thetemperature of the compressed engine air to approximately 300 degreesFahrenheit prior to further conventional cooling in the ECS 36 fordistribution to the cabin 34 as generally understood.

The deoxygenated fuel is preferably raised to a temperature whichexceeds 325 degrees Fahrenheit in the liquid-to-air heat exchangersystem 32 prior to communication to the combustor section of the ECD 12.This and greater temperatures are available due to the deoxygenationsystem 30 which permits the deoxygenated fuel to accommodatetemperatures upwards of 900 degrees Fahrenheit. The performance of theECD 12 is improved with otherwise wasted thermal energy. Moreover, theincreased cooling of the compressed air prior to communication to theECS 36 due to the air-to-liquid heat exchanger system 32 advantageouslyminimizes the size and/or weight of this and other heat exchangersassociated with the ECS 36. Such thermal management avoids or minimizesthe usage of fan bypass air which would otherwise reduce engineoperating efficiency.

Although particular step sequences are shown, described, and claimed, itshould be understood that steps may be performed in any order, separatedor combined unless otherwise indicated and will still benefit from thepresent invention.

The foregoing description is exemplary rather than defined by thelimitations within. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, one ofordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. For thatreason the following claims should be studied to determine the truescope and content of this invention.

1. A thermal management system comprising: a fuel stabilization system;a liquid-to-air heat exchanger system in fluid communication with saidfuel stabilization system; and an environmental control system incommunication with said liquid-to-air heat exchanger system.
 2. Thethermal management system as recited in claim 1, wherein said fuelstabilization system comprises a deoxygenation system.
 3. The thermalmanagement system as recited in claim 1, wherein said liquid-to-air heatexchanger is in communication with compressed air from an EnergyConversion Device.
 4. The thermal management system as recited in claim3, wherein said Energy Conversion Device is an aircraft gas turbineengine.
 5. The thermal management system as recited in claim 1, whereinsaid liquid-to-air heat exchanger is a fuel-to-air heat exchanger. 6.The thermal management system as recited in claim 1, wherein saidliquid-to-air heat exchanger operates to reduce a temperature of acompressed air to approximately 300 degrees Fahrenheit.
 7. The thermalmanagement system as recited in claim 1, wherein said liquid-to-air heatexchanger operates to reduce a temperature of a compressed air toapproximate a liquid inlet temperature of said liquid-to-air heatexchanger system.
 8. The thermal management system as recited in claim6, wherein said liquid-to-air heat exchanger operates with fuel attemperatures exceeding 325 degrees Fahrenheit.
 9. The thermal managementsystem as recited in claim 1, wherein said environmental control systemcommunicates airflow to an aircraft cabin.
 10. The thermal managementsystem as recited in claim 1, wherein said environmental control systemcommunicates airflow to an electronic device.
 11. The thermal managementsystem as recited in claim 1, wherein fuel from said liquid-to-air heatexchanger is in communication with a combustor section of a gas turbineengine.
 12. A method of thermal management comprising the steps of: (1)deoxygenating a fuel to provide a deoxygenated fuel; (2) communicatingthe fuel through a liquid-to-air heat exchanger system; (3)communicating a compressed air from an energy conversion device throughthe liquid-to-air heat exchanger system to reject heat from thecompressed air to the deoxygenated fuel; and (4) communicating thecompressed air from the liquid-to-air heat exchanger to an environmentalcontrol system.
 13. A method as recited in claim 12, wherein said step(3) further comprises the step of: drawing the compressed air from acompressor section of a gas turbine engine.
 14. A method as recited inclaim 12, wherein said step (3) further comprises the step of: rejectingheat to the deoxygenated fuel to raise the temperature of the fuel toabove approximately 325 degrees Fahrenheit.
 15. A method as recited inclaim 14, further comprising the steps of: communicating thedeoxygenated fuel from the liquid-to-air heat exchanger system to acombustor section of a gas turbine engine.